1. Field of the Invention
The present invention relates to devices for delivering therapeutic agents to one or more of the eye, nose and throat, and more particularly, to punctal plugs for delivering therapeutic agents to one or more of the eye, nose and throat.
2. Discussion of the Related Art
Human tears are secreted by the lacrimal gland and flow across the surface of the eye to a shallow pool, known as the lacrimal lake, located where the eyelids come together at their inner ends. From there, the tears drain through small openings in each of the upper and lower eyelids, termed the superior lacrimal punctum and the inferior lacrimal punctum, respectively. From the superior and inferior puncta, the tears pass into each of the superior and inferior lacrimal canaliculus, respectively, which are duct-like pathways that lead to the lacrimal sac. The lacrimal sac is the superior, expanded portion of the nasolacrimal duct, which drains tears into the nasal system. Active and/or therapeutic agents can thus be delivered to the nose and throat through the lacrimal canaliculi, which lead into the nasolacrimal duct.
Active agents frequently are administered to the eye for the treatment of ocular diseases and disorders. Conventional means for delivering active agents to the eye involve topical application to the surface of the eye. The eye is uniquely suited to topical administration because, when properly constituted, topically applied active agents can penetrate through the cornea, conjunctiva or sclera and rise to therapeutic concentration levels inside the eye. Active agents for ocular diseases and disorders may be administered orally or by injection, but such administration routes are disadvantageous in that, in oral administration, the active agent may reach the eye in too low a concentration to have the desired pharmacological effect and their use is complicated by significant, systemic side effects, while injections pose the risk of infection, discomfort, bleeding or perforation of the globe.
The majority of ocular active agents are currently delivered topically using eye drops which, though effective for some applications, are inefficient. When a drop of liquid is added to the eye, it overfills the conjunctival sac, the pocket between the eye and the lids, causing a substantial portion of the drop to be lost due to overflow of the lid margin onto the cheek. In addition, a substantial portion of the drop that remains on the ocular surface is drained into the lacrimal puncta, diluting the concentration of the drug.
To compound the problems described above, patients often do not use their eye drops as prescribed. Often, this poor compliance is due to an initial stinging or burning sensation caused by the eye drop. Certainly, instilling eye drops in one's own eye can be difficult, in part because of the normal reflex to protect the eye. Therefore, sometimes one or more drops miss the eye. Older patients may have additional problems instilling drops due to arthritis, unsteadiness, and decreased vision, and pediatric and psychiatric patient populations pose difficulties as well.
It is known to use devices that may be inserted into one or more of an orifice of an individual's eye, such as a lacrimal punctum, to deliver active agents. These punctal plugs may be configured for customized delivery of the active agents in terms of dosage and duration; however, as each individual's eye anatomy is unique, placement and anchoring of the punctal plug in the puncta may present certain difficulties. Accordingly, there exists a need for punctal plugs that are configured for ease of placement and anchoring while delivering an active agent over a predetermined treatment period.